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  3. We all have offensive breath at one time or another. In most cases offensive breath emanates from bacteria in the mouth, althoug

We all have offensive breath at one time or another. In most cases offensive breath emanates from bacteria in the mouth, althoug

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问题       We all have offensive breath at one time or another. In most cases offensive breath emanates from bacteria in the mouth, although there are other, more surprising causes.
     Until a few years ago, the most doctors could do was to counsel patients with bad breath about oral cleanliness. Now they are finding new ways to treat the usually curable condition.
      Bad breath can happen whenever the normal flow-of saliva (唾液) slows. Our mouths are full of bacteria feeding on protein in bits of food and shed tissue. The bacteria emit smelling gases, the worst of which is hydrogen sulfide (硫化物).
     Mouth bacteria thrive in airless conditions. Oxygen-rich saliva keeps their numbers down. When we sleep, for example, the saliva stream slows, and sulfide producing bacteria gains the upper hand, producing classic "morning breath".
     Alcohol, hunger, too much talking, breathing through the mouth during exercise—anything that dries the mouth produces bad breath. So can stress, though it’s not understood why. Some people’s breath turns sour every time they go on a job interview.
     Saliva flow gradually slows with age, which explains why the elderly have more bad breath trouble than younger people do. Babies, however, who make plenty of saliva and whose mouths contain relatively few bacteria have characteristically sweet breath.
     For most of us, file simple, dry-mouth variety of bad breath is easily cured. Eating or drinking starts saliva and sweeps away many of the bacteria. Breakfast often stops morning breath. Those with chronic dry mouth find that it helps to keep gum, hard candy, or a bottle of water or juice around. Brushing the teeth wipes out dry-mouth had breath because it clears away many of the offending bacteria.
     Surprisingly, one thing that rarely works is mouthwash. The liquid can mask bad-breath odor with its own smell, but the effect lasts no more than an hour. Some mouthwashes claim to kill the bacteria responsible for bad breath. The trouble is they don’t necessarily reach all offending germs. Most bacteria are well protected from mouthwash under thick layers of mucus (黏液). If the mouthwash contains alcohol—as most do—it can intensify the problem by drying out the mouth.
We can infer from this passage that _______.
选项 A、offensive breath can’t easily be cured
B、elderly people are less offended by bad breath
C、heavy drinkers are less affected by bad breath
D、offensive breath is less affected by alcohol
答案A
解析 推理题。根据上一道题，大多数的口臭根源于口腔内的细菌，但要接触到并杀死这些细菌却十分困难，从而推断出此病不易治愈。所以，A项符合文意。选项B老年人很少受到口臭的困扰”与第六段第一句的文意不符，即唾液的流速随着年龄的增长而减缓，因而老年人比青年人更易于受到口臭的困扰；选项C“酗酒者不易受口臭的影响”和选项D“酒精对口臭没有多大影响”的说法不正确，因为在上一个问题中我们已经论证过酒精对口臭有着直接的影响。
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